1. Field of the Invention
The present invention relates to an authentication system for authenticating an apparatus to be authenticated by an authentication apparatus by performing a ciphering process, an apparatus to be authenticated, an authentication apparatus, an authenticating method, a program for an apparatus to be authenticated, and a program for an authentication apparatus.
2. Description of the Related Art
Hitherto, there is a challenge-response authentication as an authenticating method using a one-way function such a hash function.
FIG. 13 shows an example of a challenge-response authentication when a server accesses a client terminal. In this case, the server is an apparatus to be authenticated, and the client terminal is an authentication apparatus.
It is assumed that a password and a number of processes “n” using a hash function are pre-stored in the server. The same password is pre-stored in the client terminal.
First, the server accesses the client terminal and transmits a challenge code and the number “n” (step S501).
The client terminal which receives the challenge code and the number “n” performs a process using a hash function on the password “n” times, thereby generating a ciphered password Kn (step S502).
The server performs a process using a hash function on the password (n−1) times, thereby generating a ciphered password Kn−1 (step S503), and transmits the password Kn−1 to the client terminal (step S504).
The client terminal performs the process using the hash function on the received password Kn−1 once thereby obtaining the ciphered password Kn, and executes an authentication by determining whether the password held by itself matches the password Kn generated at step S502 or not (step S505).
A conventional system for performing authentication gives a one-time password for a remote command when a network monitoring apparatus issues the remote command for starting an agent program of an apparatus to be monitored, performs authentication based on the one-time password, and then, starts the agent program (for example, Japanese Patent Application Laid-Open (JP-A) No. 2004-21549 (document 1)).
In another conventional system, at the time of transmitting an update packet of a profile from a management PC to a user PC, information of an encryption key is included in the update packet. The information is encrypted with a hash key, and the encrypted information is transmitted. The user PC receives the information and decrypts the information (for example, JP-A No. 2005-51625 (document 2)).
Although the conventional communication systems intend to increase the reliability of authentication by using a one-way function such as a hash function, two operations of transmitting a challenge code and transmitting Kn−1 are necessary.
There is room for simplifying procedures to decide whether the same authenticated apparatus as one used in the previous communication has established the current communication.
In addition, the same password has to be stored in both of the authenticating apparatus and the apparatus to be authenticated.
That is, in the case of authenticating that a communication was performed with the same apparatus to be authenticated, there is room for improvement in security.
In the conventional system of document 1, authentication using a one-time password is only considered.
In the conventional system of document 2, a packet encrypted with a hash key is only decrypted on the receiver's side.
Both of the conventional systems disclosed in documents 1 and 2 do not take consideration of simplification of authentication procedures such as transmission of a challenge code or of simplification of storing a password so as not to let both of the authenticating device and the authenticated device possess the password.